You may remember from our look at the history of welding that brittle, porous welds posed serious safety concerns in industrial applications. Much of the problem with those early welds stemmed from oxidation. As the science of welding advanced, methods of shielding the welding site from oxygen were developed. In stick welding, for instance, the welding rod is coated in flux. Flux serves several different purposes, one of which is to create a gas shield for the welding site as the flux is burned. MIG and TIG welding go so far as to use gas canisters that constantly envelop the welding site in inert gases. Preventing welding sites from oxidizing is crucial to forming a strong weld.
The process of joint preparation is perhaps equally important to producing strong welds. Ensuring that work materials are free of grease, dirt and dust is only the first step in properly preparing a welding joint. Edge joints, lap joints, t-joints, butt joints -- there are almost as many ways to prepare a welding joint as there are ways to weld the pieces together. Selecting the right type of joint for the job at hand is critical to producing a quality weld.
Once a weld is in place, you can check its quality in several ways. Visual inspection can reveal evidence of welding performed at the wrong speed or of current, cracks or inclusions in the weld and other problems. Welders may also inspect their work using magnetic particle testing, liquid penetration inspection, ultrasonic testing, X-ray inspection, pressure testing or other methods. Destructive testing, while destroying the weld under examination, is also frequently used to determine the quality of a weld. No matter what test is used, ensuring welds are strong and durable is an important step in the process.